The light-emitting diode (LED) luminescence technique has become popular due to the advantages of energy saving, non-radiation, long service life and the like. Particularly in the manufacturing industry of LCD devices, backlights of the LCD devices have gradually applied LEDs instead of the previously applied cold cathode fluorescent lamps (CCFL). Currently, the types of the LED backlight sources are mainly divided into direct-lit type and side-lit type, wherein side-lit type LED backlight sources are applied by more and more LCD device manufacturers due to the advantages of a small number of adopted LEDs, advantageous heat dissipation, low thickness and the like.
FIG. 1 is a schematic structural view of a side-lit type LED backlight source in the prior art.
As illustrated in FIG. 1, the side-lit type LED backlight source comprises: a light bar 10, a plurality of LED lamps 11 mounted on the light bar, and an LGP (Light Guide Plate) 13 corresponding to the LED lamps 11, wherein a plurality of dots 131 arranged at intervals are disposed on the light guide plate 13 and configured to change the direction of light emitted by the LED lamps 11 at a side by means of reflection, scattering and the like, so that the light can enter a display screen of an LCD device.
The light guide plate 13 is a necessary component of the side-lit type LED backlight source as the light guide plate 13 affects the subjective effect for the side-lit type LED backlight source: the brightness uniformity. Whether the LCD device has hotspot (brightness unevenness) and the uniformity degree of the screen brightness of the LCD device after the light guide plate 13 is applied are important evaluation criteria for the quality of the light guide plate 13.
The inventor found that: only the longitudinal distance between the LEDs and the dots 131 is considered in the diameter design of the dots 131 disposed at different positions of the traditional light guide plate 13. Since the light emitted from LEDs is weaker and weaker in the direction away from the LEDs and dots 131 with larger diameter exhibit better light-educing performance, dots 131 with larger diameter are provided more far away from the LEDs, and hence the uniformity of light emitted from the light guide plate 13 can be guaranteed as much as possible.
The schematic diagram of a light-emitting region of the LED lamp 11 as shown in FIG. 2 is obtained based on the result of the light-emitting test of the LED lamp 11 made by those skilled in the art, wherein the vertical up direction represents the 0° light-emitting direction; the horizontal left direction represents the 90° light-emitting direction; and the horizontal right direction represents the −90° light-emitting direction. As illustrated in FIG. 2, the light-emitting region of the LED lamp 11 includes a −90°-0° area A and a 0°-90° area B, and the main light-emitting region of the LED lamp 11 is ranged from −50° to 50°, wherein the intensity of the light in the 0° direction is the strongest; the intensity of the light at the angle ranges of −90° to −50° and 50° to 90° is weaker; and the 0° direction can be referred to as the central light-emitting direction of the LED lamp. However, as illustrated in FIG. 1, in the existing light guide plate 13, with regard to an LED lamp 11, as transversely arranged dots 131 on the light guide plate 13, with the same vertical distance from the LED lamp 11, have the same diameter, the intensity of the light transmitted onto dots 131 at the angle ranges of −90° to −50° and 50° to 90° of the LED lamp 11 is obviously lower than that of the light transmitted onto dots at the angle range of −50° to 50° of the LED lamp 11, thus resulting nonuniformity of the light emitted form the light guide plate 13.
Therefore, how to provide a light guide plate, a backlight source and an LCD device, with high uniformity of emergent light, is a technical problem to be solved by those skilled in the art.